This invention relates to injection molded products. More specifically, this invention relates to a manufacturing method for producing an injection molded product.
The common and most widely used manufacturing process for signage, tag and labels has been to die cut the desired size and shape of the product from rigid sheet goods material such as plastic, aluminum or steel. Thereafter, the sign blank is decorated either by printing directly on the signage, tag and label base (usually silk screen printing) or has a preprinted polymer film that has pressure sensitive glue backing with release liner. This film is prepositioned on the sign blank and the release liner removed while workers attempt to remove all air pockets and wrinkles.
In the above described processes, both of which are done at ambient temperatures and at one atmosphere of pressure, microorganisms are entrapped between the ink or film and the sign base. These microorganisms include fungi spore and pathogens that are readily emitted from the human body (the workers) and it is not difficult for these to colonize and spread into the surrounding environment given that in certain industries regular cleaning is done with high pressure hot water and harsh cleaning chemicals. The inks and labels simply deteriorate and provide the microorganisms' access to the environment. Food processing companies are a very good example but many other industries are required to meet strict state and federal sanitation requirements. These industries spend many thousands of dollars per year conforming.
Many forms of sanitation exist to combat these issues. These include exposure to UV light and specialized cleaning chemicals. But the oldest and most widely used process for sanitation is by placing objects in an autoclave. All life forms on earth require liquid water for their survival. It is also known that certain microorganisms can live and thrive in water at 212 F so the point of an autoclave is to elevate the temperature of the liquid water within microorganisms to temperatures well above 212 F. Provided below is one recommended operating procedure for an autoclave.
A widely-used method for heat sterilization is the autoclave, sometimes called a converter. Autoclaves commonly use steam heated to 121-134° C. (250-273° F.). To achieve sterility, a holding time of at least 15 minutes at 121° C. (250° F.) or three minutes at 134° C. (273° F.) is required. Additional sterilizing time is usually required for liquids and instruments packed in layers of cloth, as they may take longer to reach the required temperature (unnecessary in machines that grind the contents prior to sterilization). It requires three to five atmospheres of pressure to achieve the above noted steam and liquid temperatures.
Another process for manufacturing signages, tag and labels is to use an injection molding process. Injection molding machines are rated by their ability to generate a clamping force that holds two mold halves together against the forces of the molten thermoplastic injected at high pressure into the runner system and cavities. Clamp pressure is calculated by multiplying length by width expressed in inches times the nozzle pressure expressed in pounds per square inch divided by 2,000 pounds per ton. That entire discussion is not novel. Multi-cavity molds have been in use for many years. It does though set-up later discussion about label size and placement stability, manufacturing efficiency, gating techniques, etc.
In current injection molding machines that make indicia carriers such as labels, the labels are attached in the mold cavities. This is done by creating a static electric charge that is induced on the opened or air side of the label. This charge is of one polarity and is attracted to the opposite charged mold base thus trapping or pinning the label to the mold surface. The total static force acting to hold the label in position in the mold is a function of the total square area of the label being held. With larger labels used for signage products, this total static force is sufficient to hold the label in proper position. However, when using relative small labels that have little surface area the labels provide a relatively small total holding force and are easily dislodged from their proper position. In addition, typically the runner system provides the thermoplastics into the mold cavity nearly parallel to the label itself thus providing a force that often causes the label to be misplaced, mispositioned or completely dislodged. Further, wrinkles and bubbles often form under these labels causing the label to be improperly attached to the molded body after cure.
The fact that a label is not 100 percent fused to a sign or tag as a result of air bubbles or wrinkles underneath the label causes many problems. In an environment such as food processing facilities where tags are often used to identify containers of cleaning chemicals, the high moisture environment can cause mold and other biological growth to occur between the thermoplastic laminate of the mold and the paper label. This is unacceptable in sanitary environments.
In addition, in traditional tag manufacturing usually reinforcement is required around an attachment hole. This is accomplished by inserting and crimping either brass or steel eyelets in the hole. Simple miniature donut shaped cavities machine around the attachment hole produce a raised plastic donut around the hole on the finished product thereby reinforcing both front and rear sides of the hole. This process is time consuming and takes many man hours.
Thus, a principal object of the present invention is to provide a method of manufacturing an injection molded product that completely fuses a label to a molded body.
Yet another object of the present invention is to provide a method of manufacturing an injection molded product that is efficient and eliminates unnecessary man hours.
Another object of the present invention is to provide a method of manufacturing an injection molded product that improves a finished injection molding product.
These and other features, advantages and objective will be discussed in further detail in the specification and claims.